1. Field of the Invention
The present invention relates to a seat belt device for protecting an occupant on a vehicle in a vehicle collision and, particularly, to an inflatable belt device wherein a part of the seat belt is in a shape of an envelope and inflatable with gas from a gas generator.
2. Description of the Related Art
This type of inflatable belt device is previously known, for example, as disclosed in Unexamined Japanese Patent Publication No. H5-85301. FIG. 4 is a general perspective view of the inflatable belt device disclosed in this publication.
This inflatable belt device 1 comprises an inflatable belt 2b extending diagonally from the right side to the left side of the upper half of an occupant's body, a shoulder belt 2a connected to the inflatable belt 2b, a lap belt 3 extending from the right side to the left side of the occupant's waist, a buckle 4 arranged, for example, at a floor of a vehicle body, a tongue 5, which is inserted into and engaged with the buckle 4 when the vehicle occupant wears the seat belt, and a deflector fitting 6 for guiding the shoulder belt 2a.
The shoulder belt 2a comprises a normal webbing 2, which is the same as a typical conventional seat belt. The proximal end of the shoulder belt is connected to a seat belt retractor 7 with an emergency locking mechanism (ELR) which is fixed to the vehicle body. The shoulder belt 2a is arranged in such a manner as to be wound into the seat belt retractor 7.
The inflatable belt 2b is positioned to be in front of the chest of the occupant, and is connected to the tongue 5 at an end opposite to the end connected to the webbing 2a.
The lap belt 3 is composed of a normal webbing which is the same as a typical conventional seat belt, of which one end is connected to the tongue 5 and the other end is connected to a seat belt retractor (ELR) 8, which is fixed to the vehicle body. Further, connected to the buckle 4 is a gas generator 9, which is actuated in case of emergency such as a vehicle collision to generate high-pressure gas.
The tongue 5 and the buckle 4 are provided with passages for introducing gas from the gas generator 9 into the inflatable belt 2b. When the gas generator 9 is actuated, the gas is introduced into the inflatable belt 2b through this passages so that the inflatable belt 2b is inflated.
In the aforementioned conventional inflatable belt device, both the tongue 5 and the buckle 4 are required to have the passages for introducing gas, making the tongue 5 and the buckle 4 expensive compared to a tongue and a buckle of a normal seat belt device.